PROJECT SUMMARY The functions of vocal communication occur not just through a shared understanding of the semantics and syntax of a common language, but also through a temporal coordination of behavior between the two individuals as well. This temporal coordination emerges spontaneously in any given conversation and is known as vocal turn-taking. Given the central importance of vocal turn-taking in everyday human social interactions, it is natural to ask what are its neural bases. Understanding the neural bases of vocal turn-taking may provide insights into not only the basic mechanisms of a ubiquitous form of social interaction but may also illuminate the mechanisms that go awry in disorders that include social dysfunction. In several psychiatric disorders, like Parkinson's disease and autism, there are problems with vocal turn-taking that ultimately may lead to a lack of social connectedness. What is needed is some basic knowledge of the neural mechanisms of vocal production and perception, and their coordination during turn-taking, before we can develop a framework for investigating the underlying neural causes of behavioral impairments that limit patients' capacities to become communicatively-engaged with other individuals. We will quantitatively characterize turn-taking behavior in an animal model system and investigate its neurobiology. Specifically, we will investigate during vocal production, perception and real-time turn-taking the roles played by a medial frontal cortical structure?the anterior cingulate cortex (ACC)?and a subcortical network known as the ?social behavior network? (SBN). A handful of studies established the ACC's important role in vocal production, but none investigated ACC's role in vocal perception. The SBN is a set of interconnected subcortical areas that are common across all vertebrates and that regulates a range of social behaviors (feeding, aggression, reproduction and parental care); it includes structures such as the basal ganglia, amygdala, periaqueductal gray area and hypothalamus (among other regions). Its putative role in communication is unknown but many of its nodes overlap with those that are involved in vocal production. Our aims will 1) develop a computational model of vocal turn-taking to generate specific neural hypotheses; 2) use new imaging technology to investigate the large-scale network underlying vocal production and perception; and 3) use microstimulation and electrophysiology to directly test hypotheses gleaned from the model and imaging data.